Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 3,512,385	$ 1,522,871
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	62,157	47,908
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(15,105)	(3,602)
Securities available‑for‑sale	3,559,437	1,567,177
Government agency and government-sponsored enterprise pass through securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	759,881	515,902
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	12,075	20,142
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(4,159)	(372)
Securities available‑for‑sale	767,797	535,672
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	486,065	275,513
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,584	3,513
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(3,410)	(1,080)
Securities available‑for‑sale	486,239	277,946
Covered Private Label Collateralized Mortgage Obligation [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	24,113	26,889
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	5,794	7,153
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(125)	(95)
Securities available‑for‑sale	29,782	33,947
Other Private Label Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	115,952	10,961
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	43	46
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(981)	(93)
Securities available‑for‑sale	115,014	10,914
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,508,968	521,499
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	39,435	15,899
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,072)	(1,282)
Securities available‑for‑sale	1,547,331	536,116
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	70,196	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(816)	0
Securities available‑for‑sale	69,380	0
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	49,047	110,074
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	327	597
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(950)	(562)
Securities available‑for‑sale	48,424	110,109
Collateralized Loan Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	133,192	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	128	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,131)	0
Securities available‑for‑sale	132,189	0
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	211,946	0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	41	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(830)	0
Securities available‑for‑sale	211,157	0
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	36,302	36,232
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	611	525
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Securities available‑for‑sale	36,913	36,757
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	116,723	25,801
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	119	33
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,631)	(118)
Securities available‑for‑sale	$ 115,211	$ 25,716

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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